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Philips BX553A
This unit in for restoration will
have all electrolytic replaced, paper capacitors and carbon resistors. The
resistors are of the brown uncoated body type. After passing an initial
Dim Bulb tester power up has the radio playing directly to the 120 volt
line. The pushbuttons are a bit tentative, all bands received stations or
static (no long wire antenna attacked). This is a quick check of all
inter-stage, IF, audio and oscillator coil tests. Later alignment
may uncover questionable transformers. But this power up test sure beats
ohming out each separate transformer and coil.
All tubes passed testing with a
Heathkit IT-17 emissions tester but two. The EABC80 showed leaks and a dim
short lamp glowing on two of three tests. The UL-41 has no tester setting.
This tube will be tested in circuit. There is a good discussion of the
UL41 propose at: http://www.radiomuseum.org/r/philips_bx553a_bx_553_a.html.
Plug this URL into the Google Translate page if you don't read Dutch.
I found a broken IF slug when I
started the alignment. Once apart several I unsuccessfully tried two other
methods (Epoxy and sticky tape). Super Glue did the trick. It
securely held the slug to the screw.
Mark
the orientation. Also note how it inserts into the
cover. |
This
is filled with wax. |
Melt
the wax but not the coil form (tube). |
Tease
out the core. |
Keep
that plastic for alignment. |
This worked. |
Not shown is cleaning out the tube with a
finger held drill bit. |
The
core slipped right in. |
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The
repaired transformer back in the chassis. |
The Bass potentiometer is
ineffective. It has a set screw threaded through the shaft. I
think this may be made from Unobtainium.
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I could not locate a
replacement. I disassembled the potentiometer and cleaned it with
Denatured Alcohol and a soft tooth brush. Be careful not to scratch off
the carbon element.
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Further
cleaning of the Bass pot helped. It is functional. A touch scratchy
but functional. I use Denatured Alcohol to saturate the pot and flush out
any accumulated crud. Then followed up with regular contact cleaner.
This procedure has rescued a few pots that I have come across. The treble
control received the same treatment.
Here
are a few final pictures. The cabinet has been touched up. Scuffs
and dings have been tinted as not to stand out. It received a wet sanding,
several coats of clear lacquer and baked precisely at 105 degrees. This
cabinet was allowed to sit for seven days before I reinstalled the
guts.
With the finish still De-gassing or
hardening for the past seven days, a haze formed on the finish. I used a
slightly water dampened paper towel (almost dry) and a soft cotton cloth
to removed the haze. I did not rub with the paper towel but only applied a
light quick amount of moisture.
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